Acid Leaching Research Articles

Bioleaching of lithium from jadarite, spodumene, and lepidolite using Acidiothiobacillus ferrooxidans

Lithium (Li) is becoming increasingly important due to its use in clean technologies that are required for the transition to net zero. Although acidophilic bioleaching has been used to recover metals from a wide range of deposits, its potential to recover Li has not yet been fully explored. In this study, we used a model Fe(II)- and S-oxidising bacterium, Acidiothiobacillus ferrooxidans (At. Ferrooxidans), to extract Li from three different minerals and kinetic modelling to predict the dominant reaction pathways for Li release. Bioleaching of Li from the aluminosilicate minerals lepidolite (K(Li,Al)3(Al,Si,Rb)4O10(F,OH)2) and spodumene (LiAl(Si2O6)) was slow, with only up to 14% (approximately 12 mg/L) of Li released over 30 days. By contrast, At. ferrooxidans accelerated Li leaching from a Li-bearing borosilicate clay (jadarite, LiNaB3SiO7OH) by over 50% (over 120 mg/L) in 21 days of leaching, and consistently enhanced Li release throughout the experiment compared to the uninoculated control. Biofilm formation and flocculation of sediment occurred exclusively in the experiments with At. ferrooxidans and jadarite. Fe(II) present in the jadarite-bearing clay acted as an electron donor. Chemical leaching of Li from jadarite using H2SO4 was most effective, releasing approximately 75% (180 mg/L) of Li, but required more acid than bioleaching for pH control. Kinetic modelling was unable to replicate the data for jadarite bioleaching after primary abiotic leaching stages, suggesting additional processes beyond chemical leaching were responsible for the release of Li. A new crystalline phase, tentatively identified as boric acid, was observed to form after acid leaching of jadarite. Overall, the results demonstrate the potential for acidophilic bioleaching to recover Li from jadarite, with relevance for other Li-bearing deposits.

Revealing role of oxidation in recycling spent lithium iron phosphate through acid leaching

Revealing role of oxidation in recycling spent lithium iron phosphate through acid leaching

Enhanced Gallium Extraction Using Silane-Modified Mesoporous Silica Synthesized from Coal Gasification Slag

This study presents an innovative approach to utilize coal gasification coarse slag (CGCS) for efficient and low-cost gallium extraction. Using a one-step acid leaching process, mesoporous silica with a surface area of 258 m2/g and a pore volume of 0.15 cm3/g was synthesized. The properties of CGCS before and after acid leaching were characterized through SEM, FTIR, XRD, and BET analyses, with optimal conditions identified for maximizing specific surface area and generating saturated silanol groups. The prepared mesoporous silica demonstrated a 99% Ga(III) adsorption efficiency. Adsorption conditions were optimized, and adsorption kinetics, isotherms, and competitive adsorption behaviors were evaluated. Competitive adsorption with vanadium suggests potential application in Ga(III) extraction from vanadium-rich waste solutions. Furthermore, the recyclability of both the acid and adsorbent was explored, with the adsorbent maintaining over 85% adsorption efficiency after five cycles. The adsorption mechanism was further elucidated through SEM-EDS, XPS, and FTIR analyses. This work not only advances resource recovery from industrial waste but also offers a sustainable method for gallium extraction with industrial applications.

Overcoming clay structure challenges in lithium recovery from boron waste using high‐temperature pressure acid leaching

AbstractBoron mines contain significant amounts of lithium along with boron. After boron is extracted, lithium remains in the waste, which has a carbonate‐hosted clay‐type structure, along with other impurities. The scarcity of lithium resources and the increasing need for lithium worldwide make such resources economically important. Although the best hydrometallurgical method for the recovery of lithium trapped within the clay‐structured mineral resources is roasting with chemicals to disrupt the clay structure and acid leaching, the process is quite difficult and costly due to the high energy and chemical addition requirements. To overcome this challenge, this study proposed a high‐temperature–pressure sulphuric acid leaching process to recover lithium from the boron waste. Under the optimized conditions (liquid/solid ratio: 10, acid concentration: 1 M, temperature: 150°C, and contact time: 120 min), 100% of lithium was leached. The leaching mechanism was determined through mineral characterization (X‐ray diffractometry [XRD], X‐ray fluorescence spectrophotometer [XRF], scanning electron microscopy–energy‐dispersive X‐ray spectroscopy [SEM–EDX], Mastersizer), and a shrinking core heterogeneous kinetics model. It was found that high‐temperature–pressure sulphuric acid leaching disrupted clay structure and promoted the leaching of lithium, the leaching kinetics fit the shrinking core heterogeneous kinetics model, and was controlled by a dual mechanism with ash diffusion and chemical reactions on the particle surface. The reaction rate constants increased with increasing temperature, and the activation energy was found to be 32.17 kJ/mol.

Selective Leaching of Lithium and Beyond: Sustainable Eggshell-Mediated Recovery from Spent Li-Ion Batteries

This study introduces an innovative strategy for the selective leaching of lithium from spent Li-ion batteries. Based on thermodynamic assessments and exploiting waste eggshells as a source of calcium carbonate, an impressive 38% of lithium was dissolved selectively through mechanical milling and water leaching, outperforming conventional thermochemical methods. Afterwards, a hydrogen peroxide-assisted sulfuric acid leaching was also implemented to solubilize targeted elements (Mn, Co, Ni, and Li), with an exceptional 99% efficiency in Mn removal from the leachate using potassium permanganate and a pH range of 1.5 to 3.5. Selective separations of Co and Ni were then facilitated utilizing CYANEX 272 and n-heptane. This comprehensive study presents a promising and sustainable avenue for the effective recovery of Li and associated co-elements from spent lithium batteries.

System analysis with life cycle assessment for NiMH battery recycling.

The nickel metal hydride (NiMH) battery technology has been designed for use in electric vehicles, solar-powered applications and power tools. These batteries contain the critical and strategic raw materials cobalt, nickel and several rare earth elements (REE). When designing a battery recycling process, there are several choices to be made regarding end-products and process chemicals. The aim of this study is to investigate and compare the environmental and economic sustainability of different recycling options for NiMH batteries by taking projected market developments into consideration and by applying life cycle assessment and life cycle costing methods. The comparative study is limited to recovery of the REEs. Two hydrometallurgical processes for recovery of the REEs from the anode material are compared with extraction of REEs from primary sources in China. The processes compared are a high-temperature sulfation roasting process and a process based on hydrochloric acid leaching followed by precipitation of REE oxalates. By comparing the different recycling approaches, the hydrochloric acid process performs best. However, the use of oxalic acid has a large impact on the overall sustainability footprint. For the sulfation roasting process, the energy, sodium hydroxide and sulphuric acid consumption contribute most to the total environmental footprint. This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

Research on the Hierarchical Separation of Rare Earths and Lithium from Rare Earth Molten Salt Slag

Lithium is an important non-renewable resource, and the study of the tiered separation of rare earths and lithium from rare earth molten salt slag is an important approach to solving the current global resource shortage. This article adopts a sulfuric acid leaching process and a lithium-containing solution iron lithium extraction separation process to recover lithium from rare earth molten salt slag. The method systematically investigates the impact of sulfuric acid concentration, liquid-to-solid ratio, leaching temperature, leaching time, pH, P507 concentration, phase ratio, extraction temperature, and extraction time on the lithium extraction effect and iron lithium separation effect in rare earth molten salt slag. The results show that under the conditions of a sulfuric acid concentration of 0.9 mol/L, a liquid-to-solid ratio of 8:1 mL/g, a leaching temperature of 70 °C, a leaching time of 90 min, a pH of 0.9, a P507 concentration of 50%, a phase ratio of 5:3, an extraction temperature of 30 °C, and an extraction time of 20 min, the lithium leaching rate reaches 97.8%, and the separation of iron and lithium is fully achieved. This method can efficiently recover the valuable element lithium from rare earth molten salt slag, which is of great significance for the subsequent preparation of lithium products and the realization of a closed-loop production of rare earth alloys by molten salt electrolysis.

Study on the thermal field material of FZ-Si crystal waste graphite purified by ultrasonic enhanced acid leaching

This study examines the acid-leaching and purification process of waste graphite in the production of Czochralski monocrystalline silicon. The optimal leaching conditions are identified as a liquid-to-solid ratio of 6, a leaching temperature of 70 °C, an acid concentration of 8 mol, and a leaching time of 60 min. The use of hydrofluoric acid, sulfuric acid, and nitric acid in the acid-leaching process increases the fixed carbon content of waste graphite from ∼94 % to ∼98.5 %. To address the low fixed carbon content that cannot be achieved through conventional acid-leaching, a method combining ultrasonic intensification with hydrofluoric and hydrochloric acid leaching is proposed and successfully implemented. Under ultrasonic enhancement conditions, the leaching effect is optimal at a temperature of 60 °C, acidity of 4 mol, and leaching time of 60 min. These results demonstrate that the introduction of ultrasound significantly strengthens the acid-leaching process. The method proposed in this study not only purifies waste graphite through acid-leaching but also elucidates the reaction behavior of various impurity elements during the leaching process. Overall, these findings provide a foundational basis for the recovery of waste graphite in the thermal field.

Acid leaching of vivianite separated from sewage sludge for recovering phosphorus and iron

This paper examines the acid leaching efficiencies of Fe and P from vivianite slurry (VS, Fe3(PO4)2·8H2O), which is magnetically separated from anaerobic digested sludge, and elaborates on Fe and P reuse routes. The characteristics and dissolution behavior of raw VS in hydrochloric, sulfuric, phosphoric, oxalic, and citric acids are investigated. Results reveal that the primary impurities in VS are organic matter, other phosphate compounds, and Mg present in the vivianite crystal structure. Hydrochloric and sulfuric acids could effectively extract P (90%) from VS at an optimal hydrogen-to-phosphorus (H⁺/P) ratio of 2.5, compared with sewage sludge ash (SSA) that normally needs an H⁺/P ratio greater than 3. Hence, VS can be employed as an alternative P resource following a similar recovery route used with SSA. However, in comparison to SSA, VS use can decrease acid consumption in P extraction and the requirement for the extensive purification of cationic impurities. Furthermore, oxalic acid effectively facilitates the separation of P and Fe in VS by precipitating Fe as insoluble ferrous oxalate in acidic conditions, leading to a high Fe recovery rate of 95%. The recovery and reuse of Fe through the oxalic acid route further improves the feasibility of VS as an alternate resource.

Lithium from clay: Assessing the environmental impacts of extraction

The burgeoning electric vehicle (EV) sector in the United States (US) is expected to drive up the demand for lithium, a critical element for EV batteries. Lithium-rich clays in the Nevada desert emerge as a prospective US-based domestic source. This study employs Life Cycle Assessment (LCA) to examine the environmental aspects of extracting lithium from this source. Among the two evaluated routes, acid leaching was more energy-efficient (35 MJ/kg LCE (Lithium Carbonate Equivalent) than roasting (200 MJ/kg LCE), based on pilot plant data. When compared to conventional methods like spodumene-based extraction, acid leaching shows reductions across almost every category, with notable decreases in high-magnitude impacts like Global Warming (48 %), Freshwater Ecotoxicity (15 %), and Smog (69 %). Water consumption is the only category that increases, rising by 79 %. Insights from this study on upstream impacts of lithium from clay could help inform sourcing decisions downstream, in the battery and EV sector.

Mechanism and experimental study on the recovery of rare earth elements from neodymium iron boron waste by NaBF4 fluorination method

Pyrometallurgical recovery of rare-earth elements from NdFeB wastes is affected by the quality of the raw materials, and mixed rare-earth products add little value. Therefore, this study investigates NaBF4 fluoride roasting for the recovery of rare-earth elements and its underlying mechanisms. Reasonable roasting temperatures were determined based on thermodynamic calculations, and single-factor experiments were conducted. When roasted at 600 °C for 30 min with 65 % NaBF4, the fluorination rate of rare-earth elements reached 95.83 %. The composition of the clinker mesophase after roasting under different conditions was analyzed. At high temperatures, oxygen heteroatoms entered the crystal lattice of the rare-earth fluorides, which were subsequently removed during acid leaching, thereby reducing the recovery rate. A three-factor, three-level Box–Behnken test was conducted using the response surface methodology to analyze the effects of various factors and their interactions on the fluorination rate. Thus, an experimental basis for the recovery of rare-earth elements from NdFeB by fluoridation roasting was established. The roasting temperature had the greatest effect on the fluorination rate, followed by the roasting time and amount of NaBF4. The model predicted an optimal fluorination rate of 98.63 % when the material was roasted at 573 °C for 25 min with 59 % NaBF4. The clinker was acid-leached under optimal conditions (2.5 h at 80 °C with 9 M HCl and a liquid–solid ratio of 4 mL/g), and the fluorination rate reached 99.39 %. These results provide theoretical and experimental support for the application of pyrometallurgy in the recovery of rare-earth elements from NdFeB wastes.

Fractionation of radiogenic Pb isotopes in meteorites and their components induced by acid leaching

Fractionation of radiogenic Pb isotopes in meteorites and their components induced by acid leaching

Optimal carbofuran degradation via CWPO in NOM-doped water by a framework Cu-doped aluminate perovskite catalyst derived from aluminum saline slags

This study is the first to propose the synthesis of LayAl1–xCuxO3–δ perovskite catalysts using Al recovered from acid leaching of saline slags. The effect of parameters such as the La/Al molar ratio was explored during the synthetic process. A suite of characterization techniques—including XRF, XRD, N2 adsorption, H2-TPR, FTIR, TGA-DTA, TEM, SEM, EDX, and XPS—confirmed the successful synthesis of high-purity (up to 90 %) perovskites with La and O vacancies, and a high concentration of Cu(I) active sites dispersed within the perovskite lattice. The best catalyst was used to optimize the degradation of carbofuran (CBF) in water doped with synthetic dissolved natural organic matter (NOM) using the Fenton-like catalytic wet peroxide oxidation (CWPO) approach. The effects of catalyst concentration, H2O2 dose, and pH on catalytic performance were investigated. Degradation, mineralization (COD removal), and H2O2 consumption were maximized, while Cu leaching was minimized using a statistical desirability function for multiple responses. Optimal conditions were found to be a catalyst concentration (mg Cu/mg H2O2) of 0.234 (2.0 g L–1), an H2O2 dose of 73.3 % (0.73 times the stoichiometric dose for full COD mineralization), and a remarkable circumneutral pH of 6.2. Under these conditions, degradation reached 94.1 %, and COD mineralization was 51 % under room temperature. Notably, the perovskite catalyst exhibited remarkable stability during reuse in up to three cycles, as demonstrated by the low Cu leaching (<1.30 mg L–1).

From waste to material strategy: A closed-loop regeneration process of spent LiFePO4 batteries

A closed-loop regeneration route to recover valuable elements from spent LiFePO4 batteries is proposed. After hot-acid leaching, the leaching rates of Li, Fe and P are above 99.8 %, and the graphite powder retain in the residue with grade of 93.33 %. With iron powder cementation, 99.96 % Cu is removed from acid leaching solution to obtain sponge copper. And then 96.67 %Al and 89.30 %F are precipitated in the form of AlPO4(s) and FeF3(s) at pH = 3.75. Li, Fe and P within the purified solution are prepared as LiFePO4 precursors by co-precipitation method, and finally LiFePO4/C materials are synthesized after two-stage calcination. The recycled LiFePO4/C materials demonstrate excellent electrochemical performance with a discharge capacity of 153.1 mAh·g−1 at 0.1C and a capacity retention of 94.0 % after 500 cycles at 1C. The present recycling process provides a strategy for short and efficient regeneration of spent LiFePO4 batteries.

A new strategy toward synthesis of novel bifunctional N- and S-bearing sorbent for platinum(IV) removal from aqueous solutions and acidic leaching residue of Pt/Al2O3 catalyst

Strong incentive politics have been elaborated for promoting the recovery of precious metals from secondary resources. Solid leaching generates acidic effluents that can be pre-treated using precipitation steps for partial separation before applying sorption for metal recovery from mild acidic solutions. For this purpose, a new sorbent was designed bearing numerous N- and S-bearing reactive groups with good affinity for platinum (as chloroanionic species). Thiazole precursors were first reacted before being grafted (by free radical reaction) with triallyl cyanurate (to form CTTR sorbent). The material was characterized by a series of analytical tools (SEM, BET, FTIR, XPS, TGA, elemental analysis, and titration). The effect of pH combined with FTIR and XPS spectroscopy analyses allowed identifying the mechanisms involved in metal binding: (a) electrostatic attraction of chloroplatinate anions with protonated amine groups (especially in acidic conditions), (b) while at moderate acidic pH metal sorption proceeds through ligand exchange and chelation onto N-based and S-based groups. Optimum sorption was found at pH close to 4 (near pHpzc value). Under selected experimental conditions, the equilibrium was reached in 25–35 min. The pseudo-first order rate equation fitted well experimental profile (though the resistance to intraparticle diffusion contributes to the kinetic control). The maximum sorption capacity at room temperature reached up to 1.58 mmol Pt g−1 (at pH 4). The sorption isotherm was successfully fitted by the Temkin equation. The sorption is spontaneous and exothermic (with reduction in maximum sorption capacity reaching up to 25 %, when temperature increases to 50 °C). Optimum platinum desorption was obtained with 0.3 M HCl solution (with solid/liquid ratio 1.67 g L−1) for complete desorption and enrichment factor close to 4.6. Complete desorption was maintained over 5 cycles, while the sorption efficiency decreased by less than 3.5 % at the fifth cycle. The sorbent showed remarkable stability for PGMs (Pd(II) in addition to Pt(IV)) against alkali-earth elements or base metals (from equimolar synthetic solutions); the selectivity is driven by the preference of the reactive groups (soft base and intermediary base) for soft PGM metals against hard and borderline metal ions; this selectivity is also affected by metal speciation (formation of chloro-anionic species). The valorization of platinum from non-compliant Pt/Al2O3 catalyst was investigated after leaching with aqua regia. Platinum was precipitated from the leachate with ammonium chloride. In a second step, aluminum was removed by precipitation at pH 5. The residual solution was then treated by adsorption on CTTR: optimum separation between Pt and Al was achieved at pH ≈ 3.

An H3O-alunite method for production of smelter grade alumina from an ammonium alum solution after high-pressure acid leaching of coal fly ash

Precipitation of H3O-alunite from an ammonium alum solution using boehmite as a seed was studied. The ammonium alum solution was obtained after high-pressure leaching of mullite-type coal fly ash (CFA) with a mixture of 7.5 M H2SO4 + 40% NH4HSO4 at 200 °C. Fe(III) was extracted from the ammonium alum solution by ion exchange sorption using the Purolite S957 resin. Effects of temperature (70–90 °C), seed boehmite (100–400 g/l), ammonium alum (60–240 g/l), and precipitation duration (2–8 h) on the Al precipitation degree were evaluated. Calcination of the precipitate at 300–950 °C to obtain alumina powder was studied next. Concentration of impurities, specific surface area, phase composition, morphology, and the average particle size distribution of alumina powders were investigated. The results show that smelter grade alumina (SGA) can be obtained at optimized parameters of precipitation and calcination.

Thiourea-linked covalent triazine frameworks enable efficient and selective gold recovery from e-waste leachate

The surging electronic waste (e-waste) has been stimulating the unremitting exploration about the advanced gold recycling technology, which is of great significance to alleviate the shortage of metal resources and minimize the negative environmental impact. Herein, the thiourea-linked covalent triazine frameworks (denoted as PbTu-CTFs) have been designed and constructed by the nucleophilic substitution between cyanuric chloride (CC) and 1,4-phenylene bis(thiourea) (named PbTu) for gold recovery from the actual e-waste leachate. Benefiting from the unique structural characteristics, including large surface areas, abundant porosity, excellent chemical stability, and high-density S, N coordinative sites, the fabricated PbTu-CTFs afford ultrahigh gold adsorption capacity up to 2255 mg/g and fast kinetics, as reflected by 99 % of Au recovery efficiency within 5 min. Meanwhile, satisfactory recyclability and regeneration are maintained after six rounds of consecutive adsorption/desorption tests. Furthermore, the resulting adsorbent is well competent for highly efficient and selective gold recovery from the acidic leaching solution of wasted central processing unit (CPU), exemplify its promising actual application potential.

Unveiling electrochemical insights of lithium manganese oxide cathodes from manganese ore for enhanced lithium-ion battery performance

Implementing manganese-based electrode materials in lithium-ion batteries (LIBs) faces several challenges due to the low grade of manganese ore, which necessitates multiple purification and transformation steps before acquiring battery-grade electrode materials, increasing costs. At present, most Lithium Manganese Oxide (LMO) materials are synthesized using electrolytic manganese dioxide, and the development of new processes, such as hydrometallurgical processes is important for achieving a cost-effective synthesis of LMO materials. In this work, we develop a full synthesis process of LMO materials from manganese ore, through acid leaching, forming manganese sulfate monohydrate (MnSO4·H2O), an optimized thermal decomposition (at 900, 950 or 1000 °C) producing different Mn3O4 materials and a solid-state reaction, achieving the synthesis of LMO. The latter was used as a cathode material for LIB exhibiting a specific capacity comparable to the state-of-the-art LMO cathode with a remarkable cycling stability of 800 cycles with <20 % in capacity loss. These performances were attributed to the excellent redox reversibility of the LMO cathode, characterized by voltammetry and in operando and in situ characterization by Raman and XRD.

Dissolution of metals in NCM622 cathode through the Dissimilatory process with Na-lactate by Shewanella putrefaciens

Objectives:The objective of this study is to confirm the possibility of reduction and consequent dissolution of Li, Ni, Co, and Mn from NCM622 cathodes in spent Li-ion batteries through the anaerobic respiration with Na-lactate by Shewanella putrefaciens.Methods:The method involves using anaerobic microbial respiration to mimic dissimilatory metal oxide reduction, allowing metals to be leached from NCM622 cathodes (LiNi0.6Co0.2Mn0.2O2) under near-neutral pH conditions (~7.5).Results and Discussion:The results show that approximately 26 wt% of the total Li, Ni, Co, and Mn were successfully leached into the solution within two weeks. This approach differs significantly from conventional acidic leaching processes, offering a more environmentally friendly and sustainable alternative. In addition, we provide quantitative information regarding the dissolution of NCM622 when it is exposed in environmental systems.Conclusion:In conclusion, microbial-based metal leaching presents a novel, sustainable pathway for recovering metals from spent Li-ion batteries, addressing environmental concerns and reducing dependence on traditional energy-intensive recovery methods.

Investigating Physicochemical Methods to Recover Rare-Earth Elements from Appalachian Coals

The demand for rare-earth elements is expected to grow due to their use in critical technologies, including those used for clean energy generation. There is growing interest in developing unconventional rare-earth element resources, such as coal and coal byproducts, to help secure domestic supplies of these elements. Within the U.S., Appalachian Basin coals are particularly enriched in rare-earth elements, but recovery of the elements is often impeded by a resistant aluminosilicate matrix. This study explores the use of calcination and sodium carbonate roasting pre-treatments combined with dilute acid leaching to recover rare-earth elements from Appalachian Basin coals and underclay. The results suggest that rare-earth element recovery after calcination is dependent on the original mineralogy of samples and that light rare-earth minerals may be more easily decomposed than heavy rare-earth minerals. Sodium carbonate roasting can enhance the recovery of both light and heavy rare-earth elements. Maximum recovery in this study, ranging from 70% to 84% of total rare-earth elements, was achieved using a combination of calcination and sodium carbonate roasting, followed by 0.25 M citric acid leaching.